From the Introduction: "Successive Administrations have identified Iran as a key national security challenge. The Trump Administration encapsulated its assessment of the threat posed by Iran in a late September 2018 State Department report entitled 'Outlaw Regime: A Chronicle of Iran's Destructive Activities.' It outlines Iran's malign activities as well as a litany of other activities the Administration terms 'the Iranian regime's destructive behavior at home and abroad.' The U.S. intelligence community testified in January 2019 that 'Iran's regional ambitions and improved military capabilities almost certainly will threaten U.S. interests in the coming year, driven by Tehran's perception of increasing U.S., Saudi, and Israeli hostility, as well as continuing border insecurity, and the influence of hardliners.' An annual Defense Department report on Iran's military power required by successive National Defense Authorization Acts (NDAAs), generally contain assessments similar to those presented publicly by the intelligence community."
CRS Report for Congress, R44017
Congressional Research Service: https://crsreports.congress.gov/